Gases: Partial Pressure and Mole Fraction

Question

A mixture of krypton and nitrogen gases at a total pressure of 927 mm Hg contains krypton at a partial pressure of 391 mm Hg. If the gas mixture contains 8.30 grams of krypton, how many grams of nitrogen are present?

g N₂

Answer 1

P_total = 927 mm Hg

P_Kr = 391 mm Hg

X_Kr = 391 / 927 = 0.42

X_N2 = 1.00 - 0.42 = 0.58

8.30 g Kr x 1 mol Kr / 83.8 g = 0.099 moles Kr

0.099 mols Kr / 0.42 = x mols N₂ / 0.58 and x = 0.137 moles N₂

grams N₂ = 0.137 mols N₂ x 28 g / mol = 3.83 g N₂